Add FluidSystemType attribute to Cap Pressure Schema

FluidSystemType is a reference list and is listed as a Type for EntryPressure.

FluidSystemType needs to be a standalone attribute with the reference list of the same name, i.e.

         "FluidSystemType": {
                "type": "string",
                "pattern": "^[\\w\\-\\.]+:reference-data\\-\\-FluidSystemType:[\\w\\-\\.\\:\\%]+:[0-9]*$"
         }

Add it within TestData at the main property level (same as Permeability, Porosity, SaturationProcessMethod)